A light emitting device is disclosed in patent literature 1. The light emitting device has five LEDs disposed between output terminals of a power conversion device. Two LEDs (first LED and second LED) as a detection target and the other LEDs (third LED through fifth LED) are connected via a connection point. The power conversion device means a DC-to-DC converter 12 in patent literature 1 and LED stands for a light emitting diode.
A resistor is connected across the two LEDs as the detection target. In the light emitting device, both ends of the resistor are a detection target region which is connected to an anode electrode of the first LED and a cathode electrode of the second LED, and one end of the resistor is connected to a ground fault detection circuit via the connection point. When a ground fault occurs in the detection target region, a voltage at the connection point drops to ground potential. Hence, by detecting such a variance of the voltage using the ground-fault detection circuit, the light emitting device is capable of detecting a ground fault in the detection target region connected to the output terminal or the connection point.
The light emitting device, however, has a problem that when a ground fault is occurring at the anode of the LED, the light emitting device is incapable of detecting the ground fault before the DC-to-DC converter is activated. In other words, the light emitting device has a problem that the light emitting device is incapable of detecting a ground fault unless the DC-to-DC converter is activated.